The present invention relates to a disk array device and a battery output control method for this disk array device.
For example, a disk array device is constructed by disposing memory devices such as hard disk drives, semiconductor memory devices or the like in the form of an array. A disk array device provides logical memory regions based on an RAID (redundant array of independent inexpensive disks). These logical memory regions are also called “logical volumes” (LU: logical units).
Host computers access the logical volumes, and perform the reading and writing (I/O) of data. The exchange of data between the host computers and logical volumes is accomplished via a memory.
Such a disk array device comprises a battery in addition to a main power supply. During normal operation, the main power supply adjusts power from a commercial power source, and supplies this power to the respective necessary parts. In the case of an emergency, the battery initiates the supply of power, and supplies the required power for a specified period of time instead of the main power supply. As a result, the operation of the disk array device can be maintained for a fixed period of time (International Disclosure No. 93/24878 Pamphlet).
In the disk array device described in the abovementioned reference, the device is constructed so that power is supplied to various parts from the battery in the case of an emergency. However, no great consideration is given to the battery output control method or the like, so that there is a possibility of problems. For example, in the case of the technique described in the abovementioned reference, the battery output temporarily drops during the destage control period in which data in the memory is saved in a memory device, so that it is conceivable that the disk array device might instantaneously stop. Thus, this technique suffers from low reliability.